1. Technical Field
The present invention relates to surface-emitting type semiconductor lasers.
2. Related Art
In response to substantial increase in data amount and versatile of utility in surface-emitting type semiconductor lasers in recent years, it is desired to reduce the number of oscillation modes while maintaining a high power output. In general, the number of oscillation modes may be reduced by reducing the volume of each resonator.
It is noted that the output of a semiconductor laser increases with an increase in the current value injected, and reaches a maximum value (i.e., a rolloff point) at a certain current value. This is because, in a semiconductor laser, its gain spectrum shift with an increase in the device temperature which is caused by the current injected, and the gain reaches a maximum value at a certain temperature. When the volume of a resonator is relatively small, the temperature of the device would readily elevate, and its rolloff point is reached at a relatively low current value, such that a sufficient output or current driving range may not be obtained. When a sufficient output cannot be obtained, the driving point and the rolloff point come closer to each other, and fluctuation in the output caused by the surrounding temperature may become greater unless the driving current range is narrowed. In this connection, to prevent an increase in the device temperature, Japanese laid-open patent application JP-A-2003-86895 describes a method in which a groove reaching the current constricting section is formed around the light emitting section, and an electrode is directly formed over the groove. As a result, the distance between a heat generating section and the electrode is shortened, thereby improving the heat radiation efficiency.